To clarify my question: is the 32-bit client actually rendering at 2880 × 1800, or is it rendering at 1440 × 900 and scaling by 2?
This is an enlargement of an image rendered by the 64-bit client (in windowed mode) on my 15in, 2018 MacBook Pro. The white box encapsulates a single pixel of my computer's display. The video appears to have been scaled by 2, probably because the client doesn't support Retina displays. The 32-bit client also scales the video by 2 in windowed mode.